Why do carbon dioxide emissions weigh more than the fuel they originated from?

The amount of carbon dioxide (CO₂) produced from burning fuel weighs more than the fuel does. During complete combustion, each carbon atom in the fuel combines with two oxygen atoms in the air to make CO₂. CO₂  has an atomic weight of 44—about 3.6667 times the atomic weight of carbon, which is 12.

For example, subbituminous coal is, on average, 51% carbon. So, the carbon in a short ton (2,000 pounds) of subbituminous coal weighs 1,020 pounds. The CO₂ emissions from burning a short ton of subbituminous coal weigh approximately 3,740 pounds, or about 3.67 times the weight of the carbon and 1.87 times the weight of the coal.

Learn more:
Atomic weights of all elements in the periodic table of elements.
How much carbon dioxide is produced when different fuels are burned?

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